You can also cancel your award ticket which you've purchased using your Delta SkyMiles and cancellation should be initiated a minimum of 72 hours before the flight time of departure . There's a hard and fast cancellation charge of $150 no matter the fare type and destination. However, SkyMiles Platinum and Diamond Medallion members are exempted from the Delta cancellation policy. After cancellation, all the miles that are used for flight booking are credited into your SkyMiles account.